Have we seen a big flood?Past shows flood-prone Red has potential for larger crests
After a record Red River crest, after weeks of chucking sandbags and losing sleep over the latest forecasts, the following statement from Donald Schwert may seem hard to swallow: “We haven’t seen a big flood here,” said Schwert, a distinguished professor of geology at North Dakota State University.
By: Mike Nowatzki, INFORUM
Past shows flood-prone Red has potential for larger crests
After a record Red River crest, after weeks of chucking sandbags and losing sleep over the latest forecasts, the following statement from Donald Schwert may seem hard to swallow:
“We haven’t seen a big flood here,” said Schwert, a distinguished professor of geology at North Dakota State University.
More specifically, he said, we haven’t seen anything of the scale of the 1826 flood, which one historian described as “a calamity of the first magnitude.”
Even the flood of 1897, with its 40.1-foot crest that washed away houses and stood as the highest on record until March 28, may have been worse than this year’s 40.82-foot flood if present conditions were in place back then, he said.
The severity of Red River floods is often met with disbelief – and more than a little disdain – but their frequency shouldn’t come as a surprise.
Since 1901, when the U.S. Geological Survey began systematically recording stream flow and elevation here, the Red at Fargo has surpassed its 30-foot major flood stage in 12 different years, including this year. The river reached major flood stage five times since 1997.
The river reached its minor flood stage of 18 feet in 44 of those years.
“Bottom line is, there’s always floods, and there’s always going to be bigger floods,” said Chuck Fritz, director of the International Water Institute.
Red is relatively young
The Red River throws a lot of temper tantrums, and with a good excuse: Compared with most rivers, it’s just a toddler.
As Schwert points out, the Red River Valley is the youngest major land surface in the contiguous United States. It was exposed when glacial Lake Agassiz finished draining about 9,200 years ago, whereas most U.S. rivers are millions of years old.
“This is not a normal river setting,” he said.
The Red has several factors that make it prone to spring flooding.
A normal river occupies a channel with a floodplain on the sides and valley walls immediately adjacent to the floodplain.
The Red occupies a channel in a flat lakebed, and the nearest valley walls are miles away, allowing its floodwaters to move “as shallow sheets that meet with other shallow sheets,” Schwert said.
Unlike most U.S. rivers, the Red flows north. Spring thaw starts in the southern valley before the northern valley, causing ice jams, backwater flow and floods.
The river also slopes like a bowling lane – so gradual it’s almost imperceptible to the naked eye.
From Wahpeton, N.D., to the mouth of Lake Winnipeg, the snaking 545-mile-long river drops only 229 feet in elevation, an average of less than 6 inches per mile, according to the water institute.
That gives the river a tendency to pool, spilling out as a shallow lake 50 to 60 miles wide at times, as it did in 1997, Schwert said.
And, it’s getting worse.
Where thick and heavy glaciers once put immense pressure on the Earth’s crust, those areas are now slowly rising in a process called isostatic rebound – similar to what happens when you lift your head off a pillow, Schwert said.
Because glaciers were thicker in the northern valley, it is rebounding more than the southern valley, reducing the south-to-north slope.
“We don’t know how much longer this will occur, but assuming it’s going to occur for another few centuries anyhow, we’ll probably start to see the formation of a permanent lake north of Grand Forks,” Schwert said.
The flood of 1897
In the meantime, the valley will have to settle for the temporary lakes created by spring flooding.
Two floods often brought up as benchmarks for Fargo-Moorhead occurred in 1826 and 1897.
As news outlets have reported, the current flood broke the record for the highest Red River crest.
But which year held the record is up for debate.
The previous record of 40.1 feet was set in 1897.
However, the river gauge at that time wasn’t at 13th Avenue South in Fargo as it is now, said Steve Robinson, chief of hydrologic records and information at the USGS Water Science Center in Bismarck.
Based on work done by one of its hydrologists, the USGS believes that if the gauge had been in the same spot, the 1897 crest would have been 39.1 feet – lower than the 1997 crest of 39.6 feet, Robinson said.
“So, there’s a little bit of misunderstanding there,” he said.
In fact, the river flow in 1997 was about 3,000 cubic feet per second higher than in 1897, according to USGS records – but again, systematic river gauge records didn’t start until 1901, Robinson said. Prior to that, records are based largely on newspaper accounts and previous high-water marks used at the time, he said.
Nevertheless, the 1897 flood is worth noting, as University of North Dakota history professor Elwyn B. Robinson did in his “History of North Dakota.”
The winter of 1896-97 saw very heavy snowfall, and some towns lost train service for a week, he wrote.
“When snow melted in the spring, a great flood spread along the Missouri, James, Sheyenne, and Red Rivers,” he wrote. “It swept away property, drowned many deer, inundated towns, covered twenty-five blocks of paving in Grand Forks, damaged bridges, and made a lake thirty miles wide and a hundred and fifty miles long in the Red River Valley. Families and livestock huddled on the tops of haystacks.”
In Fargo-Moorhead, the river forced hundreds from their homes, flooded basements in residential and business districts, closed the NP railroad bridge and crippled Fargo’s water works, prompting the Moorhead Fire Department to stretch hoses across bridges to Fargo, according to newspaper accounts.
“More damage is being done in Fargo thus far than in Moorhead as in the former city the better class of houses in Island Park and throughout the southern part of the city have been flooded and a number of fine residences have been toppled over,” the Moorhead Daily News reported April 6, 1897.
The Forum reported that a young man drowned when the duck boat he was rowing hit rapids at a culvert on Eighth Street and he and two others were tossed from the boat.
1826: ‘the worst ever’
While the 1897 flood was the largest on record prior to the current flood, it may not have been the biggest of the 19th century.
That honor probably goes to 1826, which Wilson Green, former executive director of the Manitoba Historical Society, called “the worst ever experienced by white settlers in the area.”
Winnipeg marked its largest flood on record in 1826, but the flood wasn’t recorded in the U.S. portion of the Red River Basin, which had limited white settlement at that time.
Wilson, in his book “Red River Revelations,” shared a vivid account by eyewitness Alexander Ross of the 1826 flood in the present-day Winnipeg area:
“The people had to fly from their homes for dear life, some of them saving only the clothes they had on their backs.
“The shrieks of children, the lowing of cattle, and the howling of dogs added terror to the scene. … Hardly a house or building of any kind was left standing in the colony.
“… The most singular spectacle was a house in flames, drifting along in the night, its one half immersed in water, and the remainder burning furiously.”
How high the river got in Fargo-Moorhead that spring is unknown, but there’s been at least one attempt to figure it out.
A task force established by the International Joint Commission (IJC) after the 1997 flood developed a hydraulic model to simulate a scenario that would result in the 1826 flood discharges in Winnipeg.
Based on that model, the Red at Fargo would have crested at 42.5 feet.
“But there was a lot of disagreement over whether that was realistic,” said Scott Jutila, a hydraulic engineer with the Army Corps of Engineers in St. Paul.
Present-day dams, dikes, ditches and urbanization didn’t exist back then. The valley also had more prairie wetlands that acted as sponges to hold water, which now enters rivers faster, Schwert said.
“All the sponges were full (in 1826), and they still then experienced this catastrophic flood which really drowned the Red River settlement up there on the Canadian border,” he said.
Taking into account urban infringement on the flanks of the Red River, farm drainage and other factors, Schwert said the onset of conditions that led to the 1826 flood “would be absolutely catastrophic” for the F-M area today.
“We don’t have anything in place that is going to be able to handle floodwaters of that type of magnitude,” he said.
Speculating on how 1826 or 1897 flood levels would relate to today is difficult, Steve Robinson said.
“The information is so sparse that I don’t think you’d come up with reasonable results,” he said.
After the IJC task force issued its report, the corps completed a new flood frequency analysis for the Federal Emergency Management Agency for the F-M area. It found that the amount of water running through Fargo-Moorhead during a 100-year flood would be 8 percent greater than previously thought.
In the end, 1997 was figured to be a 70-year flood, and the new 100-year flood elevation was 40.8 feet.
By that standard, the F-M area this spring has already weathered the flood of the century.
But as Fritz, of the water institute, noted, the term “100-year flood” simply means there’s a 1 percent chance of a flood of that magnitude happening.
“We have the same chance next year as we did this year,” he said.
Readers can reach Forum reporter Mike Nowatzki at (701) 241-5528